In order to maintain the competitiveness of the third-generation mobile communication system in the communication field, the 3rd Generation Partnership Project (3GPP) standard working group is now concentrating on the research of Evolved Packet System (EPS). FIG. 1 shows a schematic diagram of a structure of an evolved packet domain system. As shown in FIG. 1, the entire EPS system is divided into two parts, namely a radio access network and a core network. The core network comprises a Home Subscriber Server (HSS), a Mobility Management Entity (MME), a Serving GPRS Support Node (SGSN), a Policy and Charging Rule Function (PCRF), a Serving Gateway (S-GW), a PDN Gateway (P-GW) and a Packet Data Network. The function of each part is described hereinafter.
The HSS is a site for permanently storing user subscription data and is located in the home network signed by the user.
The MME is a storage site for the user subscription data in the current network, and is responsible for non-access layer signaling management from the terminal to the network, security authentication function of the terminal, mobility management of the terminal, tracking and paging management function in user idle mode, and bearer management.
The SGSN is a service support node for the GERAN and UTRAN user to access the core network, which is similar to the mobility management entity in function, and is responsible for the functions such as user location updating, paging management, bearer management and so on.
The S-GW is a gateway from the core network to the wireless system, and is responsible for user plane bearer from the terminal to the core network, data cache in terminal idle mode, the function of the network side initiating a service request, lawful interception and functions of packet data routing and forwarding; and the S-GW is responsible for counting the situation that the user terminal uses the radio network, producing a call record of the terminal using the radio network and transmitting the call record to the charging gateway.
The P-GW is the gateway of the evolved system and the external packet data network of the system, which is connected to the Internet and the packet data network, and is responsible for functions such as Internet Protocol (IP) address allocation of the terminal, charging function, packet filtering, policy control and so on.
The packet data network is an IP service network of the operator, which provides IP services to the user through the core network of the operator.
The PCRF entity is a server in the evolved system, which is responsible for providing rules on the aspect of policies such as charging control, on-line credit control, threshold control, and Quality of Service (QoS).
A radio access network consists of E-UTRAN NodeBs (eNB) and 3G Radio Network Controllers (RNC), and is mainly responsible for transmitting and receiving radio signals, communicating with the terminal through an air interface, and managing radio resources, resource scheduling and access control of the air interface.
The above mentioned serving GPRS support node is an updated SGSN, which can support the S4 interface between the support node and the serving gateway, and communicate with the mobility management unit by the GTPv2 protocol. And for the SGSN which supports the 3G core network, the PS domain network structure is different from what is shown in FIG. 1. In this case, the SGSN and the MME are connected through the Gn interface, and communicate with each other by the GTPv1 protocol. The SGSN cannot be connected with the serving gateway, but is connected, through a Gn interface, to a Gateway GPRS Support Node (GGSN) to directly carry out packet data network access.
Home NodeB (HNB) or Home eNodeB (HeNB) is a small and low-power type of base station. As exclusive resources for some users, the Home NodeB or Home eNodeB is deployed in private places such as home, organizations, enterprises or schools, mainly serves to provide higher service rate to the users and reduce the costs of using the high rate services, and simultaneously overcome the shortage in coverage of the existing distributed cellular radio communication system. The Home NodeB has the advantages of being affordable and convenient, low-power output, plug and play, broadband access, using single-mode terminal and so on.
The Home NodeB can be applied to the 3G (3rd Generation) or the LTE (Long Term Evolution) mobile communication network. In order to facilitate the management of the Home NodeB, a new network element, namely a Home NodeB gateway, is introduced to the network. The Home NodeB gateway mainly implement the functions of: authenticating security of the Home NodeB, maintaining and managing the operation of the Home NodeB, configuring and controlling the Home NodeB according to the requirements of the operators, being responsible for exchanging data information between the core network and the Home NodeB. FIG. 2 is a 3G Home NodeB network structure diagram. The 3G Home NodeB is connected, through a newly defined Iuh interface, to the Home NodeB gateway, which provides IuPS and IuCs interfaces to the core network packet domain and circuit domain. For the 3G network, the Home NodeB gateway must be deployed so as to shield the influence of the introduction of the Home NodeB on the terminal and network side. While for the LTE network, the Home NodeB gateway is optionally deployed, thus the LTE Home NodeB can be connected to the core network in two manners, one is that the Home NodeB is directly connected to the network elements of the core network, and the other is that the Home NodeB is connected to the network elements of the core network through a gateway, as shown in FIGS. 3 and 4. As to the scene shown in FIG. 4 in which the Home NodeB gateway is introduced, the Home NodeB gateway may not integrate user plane functions, and the user plane is directly established between the Home NodeB and the user plane gateway of the core network, thus the user plane can be flattened and data transmission delay is decreased, as shown in FIG. 5.
The Home NodeB not only supports the access through the mobile core network, but also can support local access function. Under the conditions that the Home NodeB has local accessibility and the user subscription allows local access, local access of a user to other IP devices of home and enterprise networks, the Internet, or other particular networks can be realized. Through the local access function, the data offload services of the Internet or particular networks can be realized, the load of the core network is reduced, and the access to the home network device can be forwarded without the core network, which makes data transmission easy and efficient. The local access function can also be used in the macro cell, and the main use of the local access function in the macro cell is similar to that in the Home NodeB. The local access function is more applied in such scenes as local access to the Internet or to other particular networks in order to reduce the load of the core network. FIG. 6 shows the realization manner of the local access function, taking the Home NodeB scene as an example (flyback in the figure is referred to as Backhaul). The data transmitted by the user to the home network, the Internet and the core network can share a same PDN connection, the offload policy in the Home NodeB accomplishes the selection of the data packet offload path, in this case, the Home NodeB can be referred to as a traffic offload network element. The traffic offload network element is a network element having an offload policy implementing function, which can be deployed at a base station (for example, a Home NodeB, or a macro base station) or at an interface (for example, an Iu or S1 interface) between a base station and a network element of the core network. The existing traffic offload network element can use the corresponding relationship between the target address of data and the offload path selection as an offload policy. The application of this offload policy requires the traffic offload network element to perform address analysis on data packets in each bearer. The current manner in which the traffic offload network element processes data packets is not optimized, and system resources are wasted. In reality, usually only the Internet services require local access. Considering that this kind of service data does not need Qos guarantee, the data transmission can be accomplished just by using a default bearer built by user subscription Qos in the PDN connection or a dedicate bearer of non-GBR, in this case, the offload policy using bearer as granularity is more advantageous.
In addition, under the situation that the local access function of the traffic offload network element is closed or the local access function does not support mobility when the user handovers between base stations, the conventional art only can notify the network element of the core network through a special notification mechanism added by the traffic offload network element to initiate a release of the local access bearer. In the conventional art, local processing cannot be done by the traffic offload network element, which increases the burden of the core network.
In addition, in the scene that the core network side determines whether to activate the local access function, currently, there is no mechanism to notify the traffic offload network element of the state of the local access function of the user, and the traffic offload network element cannot correctly start the offload policy to perform data offload.